The teenager was found with gunshot injuries in Hughes Avenue, Bradmore, at around 4.15pm on Saturday and taken to hospital.
A gun was recovered nearby and police enquiries are being carried out to establish whether it is connected to the crime, the force said.
The incident marked the third time a gun has been fired on the region's streets in the past week – after shots were fired in Wolverhampton on Monday and in Bearwood on Wednesday.
Residents in Hughes Avenue said they heard a gunshot between 4pm and 5pm on Saturday, with the road closed and The Midlands Air Ambulance landing nearby at Bantock Park.
Residents were warned to stay inside and some nearby neighbours were evacuated.
One man, who lives on the street and did not wish to be named, said: "We heard the gunshot and then came outside and there were police everywhere.
"The ambulance came and the road was blocked off. Some of the people who live nearby in the cordon have been evacuated, and we have been told to lock our doors and stay inside."
On Monday, armed police raided a house in Colerne Street, Ettingshall, after shots were fired in nearby Hall Park Street. Then on Wednesday two men were taken to hospital after a shooting in Poplar Road, Bearwood.
A spokesman for West Midlands Police said: "We’re investigating after a woman was found with gunshot injuries in Hughes Avenue, Wolverhampton, just after 4.15pm [on April 3].
"The 18-year-old was taken to hospital with chest injuries and remains in a critical but stable condition in hospital. A gun was recovered nearby and we’re carrying out further enquiries to establish whether it’s connected.
"A scene remains in place while we continue to establish the full circumstances. Anyone with information can contact us via Live Chat, or by calling 101, and quoting log 2814 of April 3."
Alternatively, contact Crimestoppers anonymously on 0800 555111 or at crimestoppers-uk.org
